In our copending application Ser. No. 170,766, a method and apparatus for controlling the operation of a spark ignited internal combustion engine is described. In particular, the apparatus uses a knocking sensor to operate a correction signal generating apparatus in accordance with the detection of engine knocking for various engine speeds.
It is a purpose of the present invention to further develop the invention of our copending application, and particularly to optimize the generation of timing correction signals.
In our copending application there is described an apparatus wherein knocking signals are detected when the engine is operated at each of a plurality of engine speeds. The knocking signals are separately supplied to counting circuits. The value stored in the counting circuits is used for the generation of correction signals, which are combined with engine timing adjustment signals generated in an engine timing computer to correct the timing adjustment signals to avoid the occurence of engine knock. The correction signals for each operating speed of the engine are independently obtained by the detection of knocking at that particular speed range.
The invention in accordance with our copending application provides the possibility of using a control curve in the engine timing adjustment computer, which is optimized for engine operation without any attention being paid to the occurence of engine knocking. Further, the disadvantage of previous knocking control systems, wherein a saw-tooth of ignition timing is provided in response to the detecting of engine knocking is avoided. In accordance with the invention of our copending application, the control curve of the ignition timing adjustment computer is achieved advantageously with a view towards conditions actually prevailing in the engine to avoid the knocking limit, as determined by actual engine response.
As indicated in our copending application, there may occur engine speed values within the operating range of the engine at which it is difficult to acquire the necessary signals of the knocking sensor in order to derive the correction signal required for the particular speed range. Accordingly, we have described obtaining a relatively small number of correction signals, each of which is determined at a particular speed value.
It is a purpose of the present invention to provide an embodiment of the invention in our copending application, which makes it possible to obtain correction signals usable over the entire speed range of operation and which are derived by detection of knocking signals at only one particular speed range of the engine. Thus it is possible by evaluation of knocking signals in a particular speed range to derive correction signals for other speed ranges which may be otherwise difficult to obtain.